JP2005071778A - Fuel cell system and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell power generator capable of restraining the deterioration of an anode and a cathode caused by oxidation and dissolution due to a potential rise in start and stop to improve durability, and to provide its operation method. <P>SOLUTION: In stopping this fuel cell system, an oxidizer gas remaining in a fuel cell comprising an electrolyte 1, a pair of electrodes 4a and 4c and a pair of separators 7a and 7c is entirely or partially replaced with an inactive gas, and the supply of the oxidizer gas is stopped in a state that a fuel gas and the inactive gas are sealed in a stack. Since potentials of the electrodes 4a and 4c are thereby kept low, deterioration caused by oxidation and dissolution is restrained and the durability of the fuel cell system is improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell generator system that suppresses deterioration due to start-stop or improves durability, and an operation method thereof.

  The configuration and operation of a conventional general solid polymer electrolyte fuel cell will be described with reference to FIGS. FIG. 1 shows a basic structure of a polymer electrolyte fuel cell (hereinafter referred to as PEFC) among conventional fuel cells. A fuel cell is one that causes a fuel gas such as hydrogen and an oxygen-containing gas such as air to react electrochemically with a gas diffusion electrode, and generates electricity and heat simultaneously. As the electrolyte 1, a polymer electrolyte membrane that selectively transports hydrogen ions is used. A catalyst reaction layer 2 mainly composed of carbon powder carrying a platinum-based metal catalyst is disposed on both surfaces of the electrolyte 1 in close contact with each other. Reactions represented by (Chemical Formula 1) and (Chemical Formula 2) occur in this catalytic reaction layer, and a reaction represented by (Chemical Formula 3) occurs in the fuel cell as a whole.

The fuel gas containing at least hydrogen (hereinafter referred to as anode gas) undergoes the reaction shown in (Chemical Formula 1) (hereinafter referred to as anode reaction), and the hydrogen ions moved through the electrolyte 1 are converted into oxygen-containing gas (hereinafter referred to as cathode). Water is generated by the reaction shown in (Chemical Formula 2) in the catalytic reaction layer 2 (hereinafter referred to as the cathode reaction) and electricity and heat are generated at this time. As shown in (Equation 3), the fuel cell as a whole can use electricity and heat when hydrogen and oxygen react to generate water. The side in which fuel gas such as hydrogen is involved is called an anode, and a is added in the figure, the side in which oxygen-containing gas such as air is involved is called a cathode, and c is shown in the figure. Furthermore, diffusion layers 3a and 3c having both gas permeability and conductivity are disposed in close contact with the outer surfaces of the catalyst reaction layers 2a and 2c. The diffusion layers 3a and 3c and the catalyst reaction layers 2a and 2c constitute electrodes 4a and 4c. Reference numeral 5 denotes an electrode electrolyte assembly (hereinafter referred to as MEA), which is formed by the electrode 4 and the electrolyte 1. The MEA 5 is used for mechanically fixing the MEA 5 and electrically connecting adjacent MEAs 5 to each other, supplying a reaction gas to the electrodes, and carrying away a gas generated by the reaction and excess gas. A pair of conductive separators 7a and 7c, in which the gas flow paths 6a and 6c are formed on the surface in contact with the MEA 5, are disposed. A basic fuel cell unit (hereinafter referred to as a cell) includes an electrolyte 1, a pair of catalytic reaction layers 2a and 2c, a pair of diffusion layers 3a and 3c, a pair of electrodes 4a and 4c, and a pair of separators 7a and 7c. Form. The separators 7a and 7c are in contact with the separators 7c and 7a of the adjacent cells on the surface opposite to the MEA 5. The cooling water passage 8 is provided on the side where the separators 7a and 7c are in contact, and the cooling water 9 flows there. The cooling water 9 moves heat so as to adjust the temperature of the MEA 5 through the separators 7a and 7c. The MEA gasket 10 seals the MEA 5 and the separator 7a or 7c, and the separator gasket 11 seals the separators 7a and 7c.

  The electrolyte 1 has a fixed charge, and hydrogen ions exist as counter ions of the fixed charge. The electrolyte 1 is required to have a function of selectively allowing hydrogen ions to permeate. For this purpose, the electrolyte 1 needs to retain moisture. This is because when the electrolyte 1 contains moisture, the fixed charge fixed in the electrolyte 1 is ionized, and hydrogen, which is a counter ion of the fixed charge, is ionized and can move.

  The stack will be described with reference to FIG. Since the voltage of the fuel battery cell is usually as low as about 0.75 v, a plurality of cells are stacked in series so that the voltage becomes high. The current collecting plate 21 is for taking out current from the stack to the outside, and the insulating plate 22 electrically insulates the cell from the outside. The end plate 23 fastens and stacks a stack of cells.

  The fuel cell system will be described with reference to FIG. A fuel cell system is housed in the outer casing 31. The gas cleaning unit 32 removes a substance that adversely affects the fuel cell from the fuel gas, and guides the fuel gas from the outside through the raw material gas pipe 33. The valve 34 controls the flow of the raw material gas. The fuel generator 35 generates a fuel gas containing at least hydrogen from the raw material gas. The fuel gas is led from the fuel generator 35 to the stack 38 via the fuel gas pipe 37. The blower 39 guides the oxidant gas to the stack 38 through the intake pipe 40. The exhaust pipe 42 discharges the oxidant gas discharged from the stack 38 to the outside of the fuel cell system. The fuel gas that has not been used in the stack 38 flows again into the fuel generator 35 through the off-gas pipe 48. The gas from the off-gas pipe 48 is used for combustion or the like, and is used for an endothermic reaction or the like for generating a fuel gas from the raw material gas. The power circuit unit 43 extracts power from the fuel cell stack 38, and the control unit 44 controls the gas, the power circuit unit, and the like. The pump 45 causes water to flow from the cooling water inlet pipe 46 to the water path of the fuel cell stack 38. The water that has flowed through the fuel cell stack 38 is carried to the outside from the cooling water outlet pipe 47. By flowing water through the stack 38 of the fuel cell, the generated heat can be used outside the fuel cell system while maintaining the heated stack 38 at a constant temperature. The fuel cell system includes a stack 38 composed of fuel cells, a gas cleaning unit 32, a fuel generator 35, a power circuit unit 43, and a control unit 44.

  The home fuel cell system includes a fuel cell stack 38 and a fuel generator 35. It is necessary to reduce the performance degradation of the fuel cell system so that the performance can be maintained for a long time. In addition, when using raw material gas such as city gas mainly composed of methane for household use, in order to increase the utility cost and the reduction effect of CO2, the time zone when the consumption of electricity and heat is low is stopped. An operation method that operates in a time zone where consumption of electricity and heat is large is effective. In general, DSS (Daily Start & Stop or Dairy Start-up & Shut-down) operation, which operates in the daytime and stops in the middle of the night, can increase the utility cost and CO2 reduction effect. It is desirable to be able to respond flexibly to driving patterns including starting and stopping. Several reports have been made so far.

  For example, as a solution to these problems, a means for consuming electric power is separately connected in the system until starting the external load connection of the system at the start-up, thereby preventing an open circuit potential (see Patent Document 1). Moreover, the discharge means for suppression of an open circuit voltage was installed in the system (refer patent document 2). Further, in order to keep the ion exchange membrane, which is an electrolyte, in a water retaining state during storage, the humidified inert gas is sealed and stored (see Patent Document 3). In order to prevent oxidation of the oxygen electrode or adhesion of impurities, power generation is performed in a state where the supply of the oxygen-containing gas is stopped, and an oxygen consumption operation is performed to improve durability (see Patent Document 4). Further, hydrogen leaking from the anode to the cathode is used to improve the performance of the cathode electrode (see Patent Document 5).

  In addition, in order for the power generation reaction at the electrode of the fuel cell as described above to be performed stably over a long period of time, the interface between the electrolyte and the electrode needs to be stably maintained over a long period of time. The open circuit voltage of a polymer electrolyte fuel cell using hydrogen and oxygen as reactive species is theoretically 1.23V. However, the actual open circuit voltage indicates a mixed potential with impurities and adsorbed species at each of the hydrogen electrode and the oxygen electrode, and a voltage of about 0.93 V to 1.1 V. In addition, some voltage drop occurs due to diffusion of hydrogen and oxygen in the electrolyte. If there is no dissolution of impurities such as extreme metal species, the potential of the hydrogen electrode is greatly influenced by the adsorbed species of the air electrode, and the hybrid potential of the chemical reaction as shown in (Chemical Formula 4) to (Chemical Formula 8). (See Non-Patent Document 1). Thus, when the voltage exceeds 0.88 V, as shown in (Chemical Formula 7), oxidation of Pt occurs, not only the activity of Pt as a catalyst is reduced, but also dissolution in water occurs, There is a problem that flows out.

Japanese Patent Laid-Open No. 5-251101 JP-A-8-222258 JP-A-6-251788 JP 2002-93448 A JP 2000-260454 A H. Wrolowa, et al. , J. et al. Electroanal. Chem. , 15, p139-150 (1967), "Adsorption and Kinetics at Platinum Electrodes in The Presentation of Oxygen at Zero Net Current".

  However, although the conventional technique discloses a technique for preventing an open circuit, it does not describe that the voltage is 0.88V or less.

  Further, in the conventional method of purging water or humidified inert gas to the anode or cathode, it is not shown that the potential of each electrode is kept below a certain level, so the inside of the cell is filled with the inert gas. When this is done, the potentials of the anode and cathode are not determined, and gradually enter from the outside, and oxygen shows a voltage of about 0.93 V to 1.1 V at both electrodes, so the electrodes are oxidized or eluted, resulting in reduced performance. There is a problem that will let you.

  Further, in the conventional method of purging water or humidified inert gas, the temperature of the fuel cell stack 38 is lowered at the time of stoppage, condensation occurs inside the fuel cell stack 38, and the volume is reduced. Due to the negative pressure, there are problems such as external oxygen flowing in, electrolyte 1 being damaged, and electrodes 4a and 4c being short-circuited.

  In the conventional method of generating power in a state where the supply of the oxidant gas is stopped and consuming oxygen in the gas flow path 6c and then purging the gas flow path 6c with the inert gas, the gas flow path 6c There has been a problem that the electrode 4c is oxidized and deteriorated due to the influence of oxygen remaining without being consumed or air mixed in due to diffusion or leakage. In addition, since oxygen is forcibly consumed by power generation, the potential of the electrode 4c is not uniform, and the activation state of the cathode is different every time it is stopped, and the battery voltage at startup varies.

  Also, the problem that the cathode electrode performance is improved by hydrogen leaking from the anode to the cathode where air exists is that the potential becomes unstable due to the mixing of oxygen and hydrogen, and the cathode performance varies. There is.

  Moreover, the thing which improves the performance of a cathode electrode by flowing hydrogen to a cathode has the subject that the ratio of the hydrogen which is not used for electric power generation increases, and the electric power generation efficiency per energy falls.

  Further, those using nitrogen gas as an inert gas for purging have a problem that requires a special device such as a nitrogen gas cylinder.

  The present invention solves the above-described conventional problems, and replaces the oxidant gas remaining in the fuel cell with an inert gas when the voltage of the fuel cell is high and when the fuel cell is stopped, thereby oxidizing the electrode or An object of the present invention is to provide a fuel cell system capable of preventing melting and maintaining a long-term life and a method of operating the fuel cell system. Another object of the present invention is to provide a fuel cell operating method that has high power generation efficiency per energy and can maintain a long-term life. It is a third object of the present invention to provide a fuel cell operation method that can reliably improve the performance of the cathode electrode by hydrogen leaking from the anode and maintain a long-term life. Furthermore, a fourth object is to be able to supply an inert gas to the fuel cell with a simple configuration without using a special device such as a nitrogen gas cylinder.

  In order to solve the conventional problem, the fuel cell system of the present invention stops supply of oxidant gas when stopped, purges the oxidant gas inside the fuel cell with an inert gas to the fuel cell, The inert gas and the fuel gas are stopped while staying inside the fuel cell.

  As a result, the potential of each electrode is close to the potential of hydrogen gas even when stopped, and does not become high even in an open circuit state, so that deterioration during stop can be reduced. Furthermore, by adding an inert gas during stoppage, it is possible to prevent changes in pressure and potential during stoppage, and a highly durable fuel cell system can be realized even when starting and stopping.

  The fuel cell system and its operating method of the present invention suppress deterioration due to oxidation or dissolution of the electrode even when starting and stopping by replacing the oxidant gas with a gas inert to the fuel cell at the time of stop. Therefore, the life of the fuel cell system can be extended.

  A first invention is a gas flow path for supplying and discharging an electrolyte, a pair of electrodes sandwiching the electrolyte, and a fuel gas containing at least hydrogen on one of the electrodes, and an oxidant gas containing oxygen on the other A fuel cell that includes a pair of separators, a fuel generator that generates fuel gas to be supplied from the raw material gas to the fuel cell, a gas cleaning unit that removes components that adversely affect the fuel cell from the raw material gas, and a fuel In a fuel cell system having a power circuit unit that extracts power from the battery, a voltage measurement unit that measures the voltage of the fuel cell, and a control unit that controls the gas, the power circuit unit, etc., when the fuel cell is stopped, By stopping the supply of oxidant gas and replacing the oxidant gas inside the fuel cell partly or entirely with gas inert to the fuel cell, the fuel that is stopped Since there is no oxygen in the pond or less oxygen, the anode electrode has a hydrogen potential (hydrogen electrode ratio of about 0 V), and the cathode electrode also has a hydrogen potential due to the hydrogen diffused from the anode. In both cases, the potential can be kept low, so that it is possible to suppress performance degradation due to stopping.

  According to a second aspect of the invention, in particular, the fuel cell system of the first aspect of the invention is provided with a shutoff valve in the supply path and discharge path for the fuel gas and the oxidant gas, and the fuel gas and the oxidant gas are supplied when the fuel cell is stopped. Stop, replace part or all of the oxidant gas inside the fuel cell with a gas inert to the fuel cell, close the shut-off valve, and supply the fuel gas and the gas inert to the fuel cell inside the fuel cell. The fuel cell system that can be enclosed in the fuel cell shuts off the flow of gas inside and outside the fuel cell during shutdown, so the potential of the fuel cell electrode is kept low even if it is stopped for a long time. It is possible to suppress the performance degradation due to.

  In the third invention, in particular, the fuel cell system of the first invention or the second invention is provided with a humidifier in the passage of the oxidant gas and the raw material gas, and the humidified oxidant gas and the raw material gas are supplied to the fuel cell. When the raw material gas from which the components that adversely affect the fuel cell are removed in the gas cleaning section is used as an inert gas that replaces part or all of the oxidant gas Since the raw material gas can be flowed into the fuel cell and the electrolyte can be prevented from being dried, the deterioration of the performance due to the drying of the electrolyte generated during the stop can be suppressed.

  A fourth invention provides an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying / discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying / discharging an oxidant gas containing oxygen to the other A fuel cell that includes a pair of separators, a fuel generator that generates fuel gas to be supplied from the raw material gas to the fuel cell, a gas cleaning unit that removes components that adversely affect the fuel cell from the raw material gas, and a fuel In a fuel cell system having a power circuit unit that extracts power from the battery, a voltage measurement unit that measures the voltage of the fuel cell, and a control unit that controls the gas and the power circuit unit, the voltage of the fuel cell is 0.88V. If exceeded, the supply of fuel gas and oxidant gas is stopped, and the oxidant gas inside the fuel cell is partially or entirely replaced with a gas inert to the fuel cell. As a result, the potential of each electrode of the fuel cell can always be 0.88 V or less (in terms of hydrogen electrode ratio), so that oxidation and dissolution of a catalyst such as Pt can be prevented, so that the performance is maintained for a long time. It can be done.

  According to the fifth aspect of the invention, an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas for supplying / discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying / discharging an oxidant gas containing oxygen to the other A fuel cell including a pair of separators having a flow path, a fuel generator that generates fuel gas to be supplied from the source gas to the fuel cell, and a gas cleaning unit that removes components that adversely affect the fuel cell from the source gas; In a fuel cell system having a power circuit unit that extracts power from the fuel cell, a voltage measurement unit that measures the voltage of the fuel cell, and a control unit that controls the gas, the power circuit unit, etc., when the fuel cell is stopped, the fuel At the same time or after stopping the supply of gas and oxidant gas, the oxidant gas is stopped, and the oxidant gas inside the fuel cell is partially or completely replaced with a gas inert to the fuel cell. By operating the fuel cell system, since the anode electrode is filled with hydrogen (hydrogen electrode ratio), the potential of the cathode electrode is about 0 V, and the cathode electrode reduces the pressure in the path or supplies oxidant gas due to the inertia of the blower. Even if there is, after replacing with inert gas, the potential of the cathode electrode becomes about 0V (in terms of hydrogen electrode ratio) due to hydrogen diffusing from the anode. is there. Also, by stopping the fuel gas before the oxidant gas, the amount of hydrogen that is not used for power generation can be minimized, and a fuel cell system with higher power generation efficiency per energy can be realized.

  According to the sixth invention, an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas for supplying / discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying / discharging an oxidant gas containing oxygen to the other A fuel cell including a pair of separators having a flow path, a fuel generator that generates fuel gas to be supplied from the source gas to the fuel cell, and a gas cleaning unit that removes components that adversely affect the fuel cell from the source gas; In a fuel cell system having a power circuit unit that extracts power from the fuel cell, a voltage measurement unit that measures the voltage of the fuel cell, and a control unit that controls the gas and the power circuit unit, the oxidation is performed when the fuel cell is stopped. After the supply of the agent gas is stopped, the supply of the fuel gas is stopped, and the oxidant gas inside the fuel cell is partially or completely replaced with an inert gas for the fuel cell. By using the method, hydrogen flows to the anode at least for the first time when the cathode replaces the oxidant gas with an inert gas, so even if oxygen diffuses from the cathode to the anode, the potential of the anode electrode changes completely. (Hydrogen electrode ratio) is maintained at about 0V, and a sufficient amount of hydrogen diffuses to the cathode, so the potential of the cathode electrode can be quickly and reliably reduced (hydrogen electrode ratio) to about 0V. Since the performance of the cathode electrode can be reliably improved, even if the cathode electrode is stopped, the deterioration of the performance can be suppressed.

  According to the seventh aspect of the invention, an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas that supplies and discharges at least one fuel gas containing hydrogen to one of the electrodes and supplies and discharges an oxidant gas containing oxygen to the other A pair of separators having flow paths, a fuel cell having a shut-off valve in a supply path and a discharge path for fuel gas and oxidant gas, a fuel generator for generating fuel gas to be supplied from the source gas to the fuel cell, and fuel A gas purifier that removes components that adversely affect the battery from the source gas, a power circuit that extracts power from the fuel cell, a voltage measurement unit that measures the voltage of the fuel cell, and a control that controls the gas and power circuit When the fuel cell is stopped, the supply of the fuel gas is stopped, and then the fuel gas is sealed inside the fuel cell by the shut-off valve, and the supply of the oxidant gas is stopped. The oxidant gas inside the pond is partially or completely replaced with an inert gas for the fuel cell, and then the inert gas is sealed with a shutoff valve. After a certain period of time, the fuel gas sealing part and the inert gas sealing part With the operation method of the fuel cell system in which an inert gas is injected into the gas, the volume inside the fuel cell is reduced during condensation due to condensation, contraction, or the reaction between oxygen and hydrogen remaining in the fuel cell. Even if a negative pressure or a difference in pressure between the anode and the cathode occurs, the internal pressure becomes negative or the pressure difference between the anode and the cathode by injecting the inert gas into the fuel gas enclosure or the inert gas enclosure. Since the stress applied to the electrolyte or the like can be eliminated, the deterioration of the performance can be suppressed even when the operation is stopped. Further, when the inert gas is injected, the sealed gas can be replaced with the inert gas by opening the shutoff valve in the fuel gas or oxidant gas discharge path. Even when the oxygen in the air gradually enters through the gasket or the separator material while the fuel cell is stopped, it can be discharged to the outside of the fuel cell.

  According to the eighth aspect of the invention, an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and an oxidant gas containing oxygen to the other A pair of separators having flow paths, a fuel cell having a shut-off valve in a supply path and a discharge path for fuel gas and oxidant gas, a fuel generator for generating fuel gas to be supplied from the source gas to the fuel cell, and fuel A gas cleaning unit that removes components that adversely affect the battery from the source gas, a power circuit unit that extracts power from the fuel cell, a voltage measurement unit that measures the voltage of the fuel cell, and a pressure that measures the internal pressure of the fuel cell In a fuel cell system having a measurement unit and a control unit for controlling a gas, a power circuit unit, etc., when the fuel cell is stopped, the fuel gas is stopped from being supplied, and then the fuel cell is fueled inside the fuel cell by a shutoff valve The oxidant gas is shut off, the oxidant gas inside the fuel cell is partially or completely replaced with an inert gas for the fuel cell, and then the inert gas is sealed with a shut-off valve. When the internal pressure of the fuel cell changes more than a certain level, an inert gas is injected into the fuel gas enclosure and the inert gas enclosure or the shut-off valve is opened to open the space inside the fuel cell to the outside. By adopting the operation method, the gas inside the fuel cell is condensed, contracted, or remains due to the reaction between oxygen and hydrogen during stoppage, and the internal pressure is negative or the pressure between the anode and the cathode is different. Even if the gas is generated, by injecting the inert gas into the fuel gas sealing part or the inert gas sealing part, the negative pressure or the pressure difference between the anode and the cathode can be surely eliminated. Etc. The stress can be eliminated that, it can suppress a decrease in performance even if the stop. Furthermore, when the inert gas is injected, the sealed gas can be replaced with the inert gas by opening the shutoff valve in the fuel gas or oxidant gas discharge path, and the gasket and separator material can be replaced while the fuel cell is stopped. Even if oxygen in the air gradually enters through, it can be discharged to the outside of the fuel cell.

  According to the ninth aspect of the invention, an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas for supplying / discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying / discharging an oxidant gas containing oxygen to the other A pair of separators having flow paths, a fuel cell having a shut-off valve in a supply path and a discharge path for fuel gas and oxidant gas, a fuel generator for generating fuel gas to be supplied from the source gas to the fuel cell, and fuel In a fuel cell system having a gas cleaning unit that removes components that adversely affect the battery from the source gas, a power circuit unit that extracts power from the fuel cell, and a control unit that controls the gas and the power circuit unit, etc. At the time of stoppage, the supply of fuel gas is stopped, the fuel gas is sealed inside the fuel cell with a shut-off valve, the supply of oxidant gas is stopped, and the fuel cell is connected to the oxidant gas path inside the fuel cell. Then, after the inert gas is flown and the voltage of the fuel cell reaches a predetermined voltage, the anode electrode is reliably (hydrogen electrode) by adopting a method of operating the fuel cell system in which the inert gas is sealed with the shut-off valve. Can be maintained at about 0V, and the voltage can detect the cathode potential and can be reliably replaced with an inert gas until the cathode potential reaches a predetermined potential. The performance degradation can be suppressed.

  According to the tenth invention, in particular, the fuel using any of the first to ninth inventions as a gas inert to the fuel cell, using the raw material gas removed by the component gas cleaning section that adversely affects the fuel cell. By using the battery system or fuel cell system operation method, the oxidant gas can be easily replaced with an inert gas without having a special device such as a cylinder. The performance degradation can be suppressed.

(Embodiment 1)
FIG. 1 shows the basic structure of a polymer electrolyte fuel cell among the fuel cells in Example 1 of the present invention. In a fuel cell, a fuel gas containing at least hydrogen and an oxidant gas containing oxygen such as air are electrochemically reacted by a gas diffusion electrode, and electricity and heat are generated simultaneously. The electrolyte 1 is used by a polymer electrolyte membrane that selectively transports hydrogen ions. A catalyst reaction layer 2 mainly composed of carbon powder carrying a platinum-based metal catalyst is disposed on both surfaces of the electrolyte 1 in close contact with each other. Reactions represented by (Chemical Formula 1) and (Chemical Formula 2) occur in the catalytic reaction layers 2a and 2c. The fuel gas containing at least hydrogen undergoes the reaction shown in (Equation 1) (hereinafter referred to as an anode reaction), and the hydrogen ions moved through the electrolyte 1 are shown in (Equation 2) in the oxidant gas and the catalytic reaction layer 2. The reaction (hereinafter referred to as the cathodic reaction) produces water, which generates electricity and heat. The side in which fuel gas such as hydrogen is involved is called an anode, and a is added in the figure, the side in which oxidant gas such as air is involved is called a cathode, and C is shown in the figure. Furthermore, diffusion layers 3a and 3c having both gas permeability and conductivity are arranged in close contact with the outer surfaces of the catalyst reaction layers 2a and 2c, respectively. The diffusion layer 3a and the catalyst reaction layer 2a constitute an electrode 4a, and the diffusion layer 3c and the catalyst reaction layer 2c constitute an electrode 4c. An electrode electrolyte assembly (hereinafter referred to as MEA) 5 is formed of electrodes 4 a and 4 c and electrolyte 1. The MEA 5 is used for mechanically fixing the MEA 5 and electrically connecting adjacent MEAs 5 to each other in series, supplying a reactive gas to the electrode, and carrying away a gas generated by the reaction and excess gas. A pair of conductive separators 7a and 7c, in which the gas flow paths 6a and 6c are formed on the surface in contact with the MEA 5, are disposed. A basic fuel cell (hereinafter referred to as a cell) comprising an electrolyte 1, a pair of catalytic reaction layers 2a and 2c, a pair of diffusion layers 3a and 3c, a pair of electrodes 4a and 4c, and a pair of separators 7a and 7c. Form. The separators 7a and 7c are in contact with the separators 7c and 7a of the adjacent cells on the surface opposite to the MEA 5. A cooling water passage 8 is provided on the side where the separators 7a and 7c are in contact, and the cooling water 9 flows there. The cooling water 9 moves heat so as to adjust the temperature of the MEA 5 through the separators 7a and 7c. The MEA 5 and the separator 7 a or 7 c are sealed with the MEA gasket 10, and the separators 7 a and 7 c are sealed with the separator gasket 11.

  The electrolyte 1 has a fixed charge, and hydrogen ions exist as counter ions of the fixed charge. The electrolyte 1 is required to have a function of selectively allowing hydrogen ions to permeate. For this purpose, the electrolyte 1 needs to retain moisture. This is because when the electrolyte 1 contains moisture, the fixed charge fixed in the electrolyte 1 is ionized, and hydrogen, which is a counter ion of the fixed charge, is ionized and can move.

  FIG. 2 is a stack of cells and is called a stack. Since the voltage of the fuel cell is usually as low as about 0.75 v, a plurality of cells are stacked in series so as to obtain a high voltage. A current is taken out from the pair of current collecting plates 21 to the outside from the stack, the cell and the outside are electrically insulated by the pair of insulating plates 22, and the stack of the cells stacked is fastened by the pair of end plates 23. Retained.

  FIG. 3 is a configuration diagram of the fuel cell system. The fuel cell system is housed in the outer casing 31. The raw material gas taken in from the raw material gas pipe 33 from the outside is purified by the gas cleaning unit 32 that removes substances that adversely affect the fuel cell, and then guided to the fuel generator 35 through the clean gas pipe 36. A valve 34 is provided in the path of the raw material gas pipe 33 to control the flow of the raw material gas. The fuel generator 35 generates a fuel gas containing at least hydrogen from the raw material gas. Reference numeral 38 denotes a stack, which is a fuel cell and a stack whose details are shown in FIGS. Fuel gas is led from the fuel generator 35 to the stack 38 via the fuel gas pipe 37. Air as the oxidant gas is led from the outside to the stack 38 through the intake pipe 40 by the blower 39. The oxidant gas that has not been used in the stack 38 is discharged out of the fuel cell system through the exhaust pipe 42. Since the fuel cell needs moisture, the oxidant gas flowing into the stack 38 is humidified by the humidifier 41. The fuel gas that has not been used in the stack 38 flows again into the fuel generator 35 through the off-gas pipe 48. The gas from the off-gas pipe 48 is used for combustion or the like, and is used for an endothermic reaction or the like for generating a fuel gas from the raw material gas. A distribution valve 61 is provided in the clean gas pipe 36, and a distribution valve 56 is also provided in the intake pipe 40. The distribution valve 61 and the distribution valve 56 are connected to the bypass pipe 55. The distribution valve 61 adjusts the amount of gas that flows to the fuel generator 35 side after the gas purified by the gas cleaning unit 32 and the amount of gas that flows to the side of the bypass pipe 55, and the distribution valve 56 is fed from the blower 39. The purified oxidant gas and the purified raw material gas sent from the bypass pipe 55 can be mixed at an arbitrary ratio and sent to the stack 38. A shutoff valve 49 is provided in the fuel gas pipe 37 to shut off the gas flow in the fuel gas supply path of the stack 38. The off gas pipe 48 is provided with a shutoff valve 51 for shutting off the gas flow in the fuel gas discharge path of the stack 38. The shut-off valve 57 is provided in the oxidant gas supply path from the humidifier 41 to the stack 38, and blocks the gas flow in the oxidant gas supply path of the stack 38. The shut-off valve 58 is provided in the oxidant gas discharge path from the stack 38 and blocks the gas flow in the oxidant gas discharge path of the stack 38. A pressure gauge 59 is provided in the shutoff valve 49 and the fuel gas supply path of the stack 38, and the pressures of the fuel gas supply path and the fuel gas path in the stack 38 are measured. A pressure gauge 60 is provided in the oxidant gas supply path of the shut-off valve 57 and the stack 38, and the pressure in the oxidant gas supply path and the oxidant gas path in the stack 38 is measured. The voltage of the fuel cell stack 38 is measured by the voltage measuring unit 52, the electric power is taken out by the power circuit unit 43, and the gas and the power circuit unit are controlled by the control unit 44. The pump 45 causes water to flow from the cooling water inlet pipe 46 to the water path of the fuel cell stack 38, and the water that has flowed through the fuel cell 38 is carried from the cooling water outlet pipe 47 to the outside. By flowing water through the stack 38 of the fuel cell, the generated heat can be used outside the fuel cell system while maintaining the heated stack 38 at a constant temperature. The fuel cell system includes a stack 38 composed of fuel cells, a gas cleaning unit 32, a fuel generator 35, a power circuit unit 43, and a control unit 44.

  The basic operation will be described. In FIG. 3, the valve 34 is opened, and the source gas flows from the source gas pipe 33 into the gas cleaning unit 32. A hydrocarbon gas such as natural gas or propane gas can be used as the raw material gas. In this example, 13A of city gas, which is a mixed gas of methane, ethane, propane and butane gas, was used. As the gas cleaning part 32, a member for removing gas odorant such as TBM (tertiary butyl mercaptan), DMS (dimethyl sulfide), THT (tetrahydrothiofin) is used. This is because sulfur compounds such as odorants are adsorbed on the catalyst of the fuel cell to become a catalyst poison and inhibit the reaction. In the fuel generator 35, hydrogen is generated by the reaction shown in (Chemical Formula 9) or the like. The simultaneously generated carbon monoxide is removed so as to be 10 ppm or less by a shift or reaction as shown in (Chemical Formula 10) and a carbon monoxide selective oxidation reaction as shown in (Chemical Formula 11).

Here, when water is added in a minimum amount necessary for the reaction, a fuel gas containing hydrogen and moisture is created and flows into the fuel cell stack 38 via the fuel gas pipe 37. The oxidant gas passes through the humidifier 41 by the blower 39 and then flows into the stack 38. The exhaust gas of the oxidant gas is discharged to the outside through the exhaust pipe 42. As the humidifier 41, one that flows an oxidant gas into warm water, one that blows water into the oxidant gas, and the like can be used. In this embodiment, a total heat exchange type was used. In this case, when water and heat in the exhaust gas pass through the humidifier 41, they are carried from the intake pipe 40 and moved into the oxidant gas as the raw material. The cooling water flows from the cooling water inlet pipe 46 to the water path of the fuel cell stack 38 from the pump 45, and then the water is carried to the outside from the cooling water outlet pipe 47. Although not shown in the figure, the cooling water inlet pipe 45 and the cooling water outlet are connected to the transfer pipe 47 by a device for accumulating or using heat such as a normal water heater. The heat generated in the fuel cell stack 38 is taken out and can be used for hot water supply or the like. In the power generation in the stack 38, the voltage is measured by the voltage measurement unit 52, and when the control unit 44 determines that sufficient power generation is being performed, the power circuit unit 43 extracts power. The power circuit unit 43 converts the DC power extracted from the stack 38 into AC and is connected to a power line used at home or the like by so-called grid interconnection. The operation of the fuel cell in the stack 38 will be described with reference to FIG. An oxygen-containing gas such as air is flowed through the gas flow path 6C, and a fuel gas containing hydrogen is flowed through the gas flow path 6a. Hydrogen in the fuel gas diffuses through the diffusion layer 3a and reaches the catalytic reaction layer 2a. In the catalytic reaction layer 2a, hydrogen is divided into hydrogen ions and electrons. The electrons are moved to the cathode side through an external circuit. The hydrogen ions permeate the electrolyte 1 and move to the cathode side and reach the catalytic reaction layer 2C. Oxygen in the oxidant gas such as air diffuses in the diffusion layer 3C and reaches the catalytic reaction layer 2C. In the catalytic reaction layer 2C, oxygen reacts with electrons to form oxygen ions, and the oxygen ions react with hydrogen ions to generate water. That is, oxygen-containing gas and fuel gas react around MEA 5 to generate water, and electrons flow. Further, heat is generated during the reaction, and the temperature of MEA 5 rises. Therefore, the heat generated in the reaction is carried out by water by flowing water or the like through the cooling water paths 8a and 8c. That is, heat and current (electricity) are generated. At this time, it is important to control the humidity of the introduced gas and the amount of water generated by the reaction. When there is little moisture, the electrolyte 1 is dried and the ionization of the fixed charge is reduced, so that the movement of hydrogen is reduced, so that the generation of heat and electricity is reduced. On the other hand, if there is too much water, water accumulates around the MEA 5 or around the catalyst reaction layers 2a and 2c, and the gas supply is inhibited and the reaction is suppressed, so that the generation of heat and electricity is reduced. (Hereafter, this state is called flatting.)
The operation after reacting in the fuel cell will be described with reference to FIG. Exhaust gas in which the oxidant gas is not used is transferred to the oxidant gas sent from the blower 39 through the humidifier 41 and then discharged to the outside. The off gas that has not been used for the fuel gas flows again into the fuel generator 35 through the off gas pipe 48. The gas from the off gas pipe 48 is used for combustion in the fuel generator 35. Since the reaction for generating the fuel gas from the raw material gas is an endothermic reaction as shown by (Chemical Formula 9), it is used as heat necessary for the reaction. The power circuit 43 serves to draw DC power from the stack 38 after the fuel cell starts power generation. The controller 44 controls the other parts of the fuel cell system so as to keep the control optimal. When it is desired to stop the operation of the fuel cell, the distribution valve 56 and the distribution valve 61 are operated, and the raw material gas purified by the gas purification unit 32 is flowed into the stack 38. In this embodiment, in FIG. 1, the MEA 5 was created as follows.

  Carbon powder acetylene black (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd., particle size 35 nm) was mixed with an aqueous dispersion of polytetrafluoroethylene (PTFE) (D1 manufactured by Daikin Industries, Ltd.) and dried. A water repellent ink containing 20% by weight of PTFE was prepared. This ink is applied and impregnated on carbon paper (TGPH060H manufactured by Toray Industries, Inc.) serving as a base material for the gas diffusion layer, heat treated at 300 ° C. using a hot air dryer, and the gas diffusion layer (about 200 μm). ) Was formed.

  On the other hand, 66 parts by weight of a catalyst body (50 wt% Pt) obtained by supporting a Pt catalyst on Ketjen Black (Ketjen Black EC, Ketjen Black International Co., Ltd., particle size 30 nm), which is carbon powder. Is mixed with 33 parts by weight (polymer dry weight) of perfluorocarbon sulfonic acid ionomer (5% by weight Nafion dispersion manufactured by Aldrich, USA) which is a hydrogen ion conductive material and a binder, and the resulting mixture is molded. Thus, a catalyst layer (10 to 20 μm) was formed.

  The gas diffusion layer and the catalyst layer obtained as described above were bonded to both surfaces of a polymer electrolyte membrane (Nafion 112 membrane manufactured by DuPont, USA) to produce MEA5.

  Next, a rubber gasket plate was joined to the outer periphery of the electrolyte 1 of the MEA 5 produced as described above, and manifold holes for circulating cooling water, fuel gas, and oxidant gas were formed.

  On the other hand, a conductive separator plate 7 made of a graphite plate impregnated with a phenol resin, having an outer dimension of 20 cm × 32 cm × 1.3 mm and having a gas flow path and a cooling water flow path having a depth of 0.5 mm. Using.

  The details and operation method of this embodiment will be described with reference to the flowchart of FIG. In the present embodiment, the fuel gas cleaned by the gas cleaning unit 32 is used as the inert gas. Since the main component of the fuel gas is methane gas, the polymer electrolyte fuel cell used in this embodiment has little reactivity and can be treated as an inert gas. First, the fuel cell system shown in FIG. 3 generates power and generates heat (operation process). In (operation process), 13A gas of city gas was used as the source gas, and air was used as the oxidant gas. The temperature of the fuel cell stack 38 was 70 ° C., the fuel gas utilization rate (Uf) was 70%, and the oxygen utilization rate (Uo) was 40%. The fuel gas and air were humidified so as to have dew points of 65 ° C. and 70 ° C., respectively, and a current of a certain voltage was taken out from the power circuit unit 43 as power. The current was adjusted so that the current density was 0.2 A / cm 2 with respect to the apparent area of the electrode. Although not shown in the cooling water inlet pipe 46 and the cooling water outlet pipe 47, the temperature of the water in the cooling water inlet pipe 46 to which the hot water storage tank is attached is 70 ° C., and the temperature of the water in the cooling water outlet pipe 47. The pump 45 was adjusted to 75 ° C. The other conditions were as follows. The (operation process) was followed by (stop process 1). In (stop step 1), the shutoff valve 49 is first closed to stop the supply of fuel gas to the stack 38, or the blower 39 is stopped simultaneously with the stop of the supply of fuel gas to the stack. All the fuel gas is allowed to flow into the bypass pipe 55, and the gas flowing into the stack 38 by the distribution valve 57 is adjusted so that the gas from the bypass pipe 55 is all. As a result, the oxidant gas is replaced with the raw material gas as the inert gas. In this example, the source gas to be replaced was 2 to 5 times the volume to be replaced. This is based on the following calculation.

  If the volume to be replaced is V (L), the flow rate of the gas to be replaced is v (L / min), the initial concentration of the target component of the oxidant gas is co, and the concentration after t (min) time is c (calculation) As expressed by the equation (1), the concentration change dc in the volume V during the minute time dt becomes equal to the amount of the target component pushed out by the replacement gas during the minute time dt.

  After multiplying both sides by −1, taking the logarithm of both sides gives (Calculation Formula 2).

  If it arranges, it will become (calculation formula 3), and if it integrates, it will become (calculation formula 4). Here, x is an integral constant.

  (Calculation Formula 4) can be rewritten as (Calculation Formula 5).

  Here, when t = 0, c = co. Therefore, when substituting into (Equation 5), (Equation 6) is obtained.

  Therefore, (Calculation Formula 6) is substituted into (Calculation Formula 5) to be (Calculation Formula 7).

  In (Equation 7), v · t / V represents how many times the volume of the gas to be replaced is larger than the volume to be replaced. If double, 86% or more will be replaced, and if 5 times, 99.3% or more will be replaced. This is because when the volume of the replacement gas is 2 times or less, the remaining amount of the oxidant gas increases, and when the volume exceeds 5 times, the replacement gas is wasted. In (stop step 1), the supply of fuel gas is stopped earlier than or simultaneously with the stop of supply of oxidant gas, so that the power generation efficiency per fuel energy can be increased without wasting fuel gas. . After the replacement gas has flowed a predetermined amount, (stop process 2) is performed. That is, the valve 34 is closed and the whole is stopped. The drawing of current from the stack 38 may be the same as the stop of the blower 39 in (stop process 1), but the power circuit unit 43 may be controlled with a predetermined voltage. In this embodiment, when the voltage per unit cell of the stack 38 is 0.5 V or higher, the current is drawn by the power circuit unit 43, and when the voltage is lower than 0.5 V, the current is not drawn. If stopped in (stop step 2), the catalytic reaction layer 2a is filled with a gas containing hydrogen, so the potential becomes (hydrogen electrode ratio) 0V. The catalyst reaction layer 2c is filled with a raw material gas which is an inert gas, but since hydrogen diffuses through the electrolyte 1, the potential becomes (hydrogen electrode ratio) 0V. Therefore, both electrodes can be stopped without becoming a high potential at which oxidation or dissolution occurs, so that there is little deterioration and the performance can be maintained for a long time. In the present embodiment, the raw material gas cleaned in the gas cleaning section was used as the inert gas. This is convenient because it uses a source gas and can be produced without a special device. However, the same effect can be obtained even if a nitrogen gas cylinder or the like is used and an inert gas such as nitrogen gas is used. Moreover, in the present Example, the raw material gas as an inert gas was humidified with the humidifier 41 provided in the passage path of oxidant gas and fuel gas. By providing the humidifier 41 in the common passage path for the oxidant gas and the fuel gas, it is possible to humidify different gases from one humidifier, which is more effective. Moreover, the source gas as an inert gas was humidified. Even if there is no humidification, the effect is slight if the volume supplied to the stack 38 is relatively small. However, if the volume supplied is large, the electrolyte 1 is dried and the permeability of hydrogen ions is reduced. did.

(Embodiment 2)
The operation method of the present embodiment will be described using the flowchart of FIG. The basic configuration and operation are the same as those in the first embodiment. The detailed operation method is shown below. (Operation process) is the same as in the first embodiment. Next, (stop process 1) was performed. In (stop step 1), the blower 39 is first stopped, and the fuel gas after purification is made to flow to both the bypass pipe 55 and the clean gas pipe 36 by the distribution valve 61, and the gas flowing into the stack 38 by the distribution valve 56 Adjusts the gas from the bypass pipe 55 to be all. As a result, the fuel gas flows into the stack 38 and the oxidant gas in the stack 38 is replaced with the raw material gas as the inert gas. It moves after a predetermined time (stop process 2). In (stop process 2), the shut-off valves 57 and 58 are closed, and a raw material gas as an inert gas is sealed inside the stack 38. In (stop process 2), since fuel gas is supplied, hydrogen is also supplied. Since the source gas is sealed, the hydrogen that diffuses the electrolyte 1 from the fuel gas and moves to the source gas side stays in the vicinity of the catalyst reaction layer 2c. As a result, the potential of the electrode 4c can be lowered more quickly and reliably, so that deterioration of the electrode can be suppressed more reliably. (Stop process 2) may be performed for a predetermined time, but in the present embodiment, after the voltage per unit cell of the stack becomes 0.1 V or less, the process proceeds to (stop process 3). In the present embodiment (stop process 2), the electrode 4a is always 0 V, so the cell voltage is equal to the potential of the electrode 4c. When the electrode 4c becomes 0.1V, it can be said that the potential of the electrode 4c is surely lowered by the diffused hydrogen, and the fuel gas can be used without excess or deficiency, so that the power generation efficiency per energy is increased. In the next (stop step 3), the shut-off valves 49 and 51 are closed and the fuel gas is sealed in the stack. In the present embodiment, since the fuel gas and the raw material gas are sealed by the shut-off valve, since the gas does not enter and exit due to convection in the state of (stop process 3), the potentials of the electrodes 4a and 4c can be kept low. Since the deterioration due to oxidation and dissolution is less, the performance can be maintained for a longer period. Further, the process proceeds to (stop process 4). Although the stack 38 does not enter or exit from the outside due to gas convection or the like by the shut-off valves 49, 51, 57 and 58, oxygen or the like slightly diffuses from the outside. Therefore, the raw material gas cleaned by the gas cleaning unit 32 is caused to flow to both the bypass pipe 55 and the clean gas pipe 36 by the distribution valve 61 at regular intervals. Here, the shutoff valves 57 and 58 are slightly opened, the raw material gas that has passed through the bypass building 55 is sent to the stack 38, and is slightly replaced with the sealed gas. The raw material gas that has passed through the clean gas pipe 36 is sent to the fuel generator 35. By selecting a certain time so that the reaction does not occur in the fuel generator 35 or at a temperature, the fuel generator 35 remains as the raw material gas. Can be passed. Here, the shutoff valves 49 and 51 are slightly opened, and the sealed fuel gas is slightly replaced with the raw material gas. As a result, the concentration of gas such as oxygen that has entered from the outside during the encapsulation can be reduced and the potential increase of the electrodes 4a and 4c can be suppressed for a long period of time. Deterioration due to oxidation or dissolution can be suppressed, and long-term performance can be maintained.

(Embodiment 3)
The operation method of the present embodiment will be described using the flowchart of FIG. The basic configuration and operation are the same as those in the first or second embodiment. The detailed operation method is shown below. The basic conditions for power generation and heat generation (operation process) are the same as those in the first embodiment. Here, the current drawn from the stack 38 by the power circuit unit 43 is controlled by the control unit 44 in accordance with the amount of power consumed at home or the like. When the electric power generated from the fuel cell system is not consumed, the current drawn from the stack 38 decreases, and the voltage rises. If the voltage exceeds 0.88V, oxidation and dissolution of the electrode 4c occur, and the process proceeds to (stopping step 1). That is, since the operation in a state where the voltage exceeds 0.88 V can be eliminated, the performance can be maintained for a long time. In (stop process 1), the blower 39 is first stopped, and the fuel gas after purification is caused to flow to both the bypass pipe 55 and the clean gas pipe 36 by the distribution valve 61, and the gas flowing into the stack 38 by the distribution valve 57 is It adjusts so that the gas from the bypass pipe 55 may become all. As a result, the fuel gas flows into the stack 38 and the oxidant gas in the stack 38 is replaced with the raw material gas as the inert gas. It moves after a predetermined time (stop process 2). In (stop process 2), the shutoff valves 49 and 51 are closed while the raw material gas is flowing, and the fuel gas is sealed in the stack 38. Thereby, the use of fuel gas can be reduced. Further, the process proceeds to (stop process 3). The shut-off valves 57 and 58 are closed, and a raw material gas as an inert gas is sealed inside the stack 38. Hydrogen that has diffused the electrolyte 1 from the fuel gas and moved to the raw material gas side stays in the vicinity of the catalytic reaction layer 2c. Thereby, since the electric potential of the electrode 4c can be reliably lowered | hung, deterioration of an electrode can be suppressed reliably. In the state of (stopping step 3), gas does not enter or exit due to convection, etc., so the potentials of the electrodes 4a and 4c can be kept low, so that deterioration due to oxidation and dissolution is small, so long-term performance can be maintained. is there. Further, the process proceeds to (stop process 4).

  In (stop process 4), changes in pressure gauges 59 and 60 are monitored. Since the shut-off valves 49, 51, 57 and 58 are closed, if the humidity component in the enclosed gas causes dew condensation or the like due to a decrease in the temperature of the stack, the volume of the gas is reduced, and the internal pressure is negative. become. When the internal pressure of the stack 38 becomes negative, not only gas such as air is likely to enter, but the electrolyte 1 and various gaskets may be damaged. Therefore, when the values measured by the pressure gauges 59 and 60 change more than a certain value, the shut-off valve 49 or 57 is opened to add the raw material gas. In this embodiment, the operation is performed when the pressure changes by 50 KPa. The operation of flowing the raw material gas through the stopped stack 38 is the same as in the second embodiment. When the pressure inside the stack 38 reaches a predetermined value, the shutoff valve 49 or 57 is closed and the gas is sealed again. When the raw material gas is added to the fuel gas, the hydrogen concentration is reduced. However, since the entry of a gas having a high potential such as oxygen is excluded, the potentials of the electrodes 4a and 4c can be kept low. Thereby, not only deterioration due to electrode oxidation or dissolution can be suppressed, but also damage to the constituent material of the stack 38 due to pressure change can be prevented, so that high performance can be maintained for a long period of time.

  INDUSTRIAL APPLICABILITY The fuel cell system and the operation method of the present invention have an effect of suppressing deterioration due to start / stop or improving durability, and are useful for power generation apparatuses and devices using a polymer electrolyte membrane.

  Further, since a source gas such as city gas is used as the inert gas, it is useful for a stationary fuel cell cogeneration system.

Structure diagram showing a part of a unit cell of a fuel cell in Embodiments 1, 2, and 3 of the present invention and a conventional example Structure diagram of a stack in which fuel cells according to Embodiments 1, 2, and 3 of the present invention and conventional examples are stacked The block diagram which shows the fuel cell system in Embodiment 1,2,3 of this invention 1 is a flowchart showing a method for operating a fuel cell system according to Embodiment 1 of the present invention. Flowchart showing the operation method of the fuel cell system in Embodiment 2 of the present invention. Flowchart showing the operation method of the fuel cell system in Embodiment 3 of the present invention. Configuration diagram showing a conventional fuel cell system

Explanation of symbols

1 Electrolyte 2a Catalytic reaction layer (anode side)
2c Catalytic reaction layer (cathode side)
3a Diffusion layer (anode side)
3c Diffusion layer (cathode side)
4a Electrode (Anode side)
4c electrode (cathode side)
7a Separator (Anode side)
7c Separator (cathode side)
32 Cleaner 35 Fuel Generator 41 Humidifier 43 Power Circuit Unit 44 Control Unit 52 Voltage Measurement Unit 49, 51, 57, 58 Shutoff Valve 59, 60 Pressure Measurement Unit

Claims (10)

A pair of electrodes having an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying and discharging an oxidant gas containing oxygen to the other A fuel cell including a separator, a fuel generator that generates fuel gas to be supplied from the source gas to the fuel cell, a gas cleaning unit that removes components that adversely affect the fuel cell from the source gas, and power from the fuel cell In a fuel cell system having a power circuit unit to be taken out, a voltage measuring unit for measuring the voltage of the fuel cell, and a control unit for controlling the gas, the power circuit unit, etc., when the fuel cell is stopped, the fuel gas and the oxidant gas A fuel cell system in which the supply is stopped and the oxidant gas inside the fuel cell is partially or entirely replaced with a gas inert to the fuel cell. Provided with shutoff valves in the fuel gas and oxidant gas supply path and discharge path, the supply of fuel gas and oxidant gas is stopped when the fuel cell is stopped, and the oxidant gas inside the fuel cell is inactive to the fuel cell. The fuel cell system according to claim 1, wherein a part or all of the gas is substituted, the shutoff valve is closed, and the fuel gas and a gas inert to the fuel cell can be sealed in the fuel cell. The fuel cell system according to claim 1 or 2, wherein a humidifier is provided in a passage path for the oxidant gas and the raw material gas, and the humidified oxidant gas and the raw material gas can be supplied to the fuel cell. A pair of electrodes having an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying and discharging an oxidant gas containing oxygen to the other A fuel cell including a separator, a fuel generator that generates fuel gas to be supplied from the source gas to the fuel cell, a gas cleaning unit that removes components that adversely affect the fuel cell from the source gas, and power from the fuel cell In a fuel cell system having a power circuit unit to be taken out, a voltage measuring unit for measuring the voltage of the fuel cell, and a control unit for controlling the gas, the power circuit unit, etc., the fuel gas when the voltage of the fuel cell exceeds 0.88V And a method of operating the fuel cell system in which the supply of the oxidant gas is stopped and the oxidant gas inside the fuel cell is partially or entirely replaced with a gas inert to the fuel cell. A pair of electrodes having an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying and discharging an oxidant gas containing oxygen to the other A fuel cell including a separator, a fuel generator that generates fuel gas to be supplied from the source gas to the fuel cell, a gas cleaning unit that removes components that adversely affect the fuel cell from the source gas, and power from the fuel cell In a fuel cell system having a power circuit unit to be taken out, a voltage measuring unit for measuring the voltage of the fuel cell, and a control unit for controlling the gas, the power circuit unit, etc., when the fuel cell is stopped, the fuel gas and the oxidant gas At the same time or after stopping the fuel gas, the oxidant gas is stopped, and the oxidant gas inside the fuel cell is partially or entirely replaced with a gas inert to the fuel cell. Temu method of operation. A pair of electrodes having an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying and discharging an oxidant gas containing oxygen to the other A fuel cell including a separator, a fuel generator that generates fuel gas to be supplied from the source gas to the fuel cell, a gas cleaning unit that removes components that adversely affect the fuel cell from the source gas, and power from the fuel cell In a fuel cell system having a power circuit unit to be taken out, a voltage measuring unit for measuring the voltage of the fuel cell, and a control unit for controlling the gas and the power circuit unit, the supply of the oxidant gas is stopped when the fuel cell is stopped. Thereafter, the fuel gas supply is stopped, and the oxidant gas inside the fuel cell is partially or entirely replaced with a gas inert to the fuel cell. A pair of electrodes having an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying and discharging an oxidant gas containing oxygen to the other A separator, a fuel cell provided with a shutoff valve in the supply path and discharge path of fuel gas and oxidant gas, a fuel generator that generates fuel gas to be supplied from the raw material gas to the fuel cell, and a component that adversely affects the fuel cell A fuel cell having a gas cleaning unit that removes gas from the source gas, a power circuit unit that extracts power from the fuel cell, a voltage measurement unit that measures the voltage of the fuel cell, and a control unit that controls the gas and the power circuit unit In the system, when the fuel cell is stopped, the supply of the fuel gas is stopped, then the fuel gas is sealed inside the fuel cell with a shut-off valve, the supply of the oxidant gas is stopped, and the acid inside the fuel cell is stopped. After replacing a part or all of the agent gas with an inert gas for the fuel cell, the inert gas is sealed with a shut-off valve, and after a certain period of time, the inert gas is sealed in the fuel gas sealing portion and the inert gas sealing portion. Of fuel cell system for injecting fuel. A pair of electrodes having an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying and discharging an oxidant gas containing oxygen to the other A separator, a fuel cell provided with a shutoff valve in the supply path and discharge path of fuel gas and oxidant gas, a fuel generator that generates fuel gas to be supplied from the raw material gas to the fuel cell, and a component that adversely affects the fuel cell A gas cleaning unit that removes the gas from the source gas, a power circuit unit that extracts power from the fuel cell, a voltage measurement unit that measures the voltage of the fuel cell, a pressure measurement unit that measures the pressure inside the fuel cell, In a fuel cell system having a control unit for controlling a power circuit unit and the like, when the fuel cell is stopped, the supply of the fuel gas is stopped, and then the fuel gas is sealed inside the fuel cell by a shut-off valve. The supply of the oxidant gas is stopped, and the oxidant gas inside the fuel cell is partially or completely replaced with an inert gas for the fuel cell. When the pressure of the fuel cell changes more than a certain level, an operation method of the fuel cell system in which an inert gas is injected into the fuel gas enclosure and the inert gas enclosure or a shut-off valve is opened to open the space inside the fuel cell to the outside. A pair of electrodes having an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying and discharging an oxidant gas containing oxygen to the other A separator, a fuel cell provided with a shutoff valve in the supply path and discharge path of fuel gas and oxidant gas, a fuel generator that generates fuel gas to be supplied from the raw material gas to the fuel cell, and a component that adversely affects the fuel cell In a fuel cell system having a gas purifier that removes gas from the raw material gas, a power circuit that extracts power from the fuel cell, and a controller that controls the gas and power circuit, the fuel gas is After the supply is stopped, the fuel gas is sealed inside the fuel cell with the shut-off valve, the supply of the oxidant gas is stopped, and the oxidant gas path inside the fuel cell is inactive to the fuel cell. Flowing scan, after the voltage of the fuel cell becomes a predetermined voltage, the method of operating a fuel cell system that encapsulates the inert gas shut-off valve. 10. The fuel cell system or the fuel cell system operating method according to claim 1, wherein a raw material gas removed by a component gas cleaning unit that adversely affects the fuel cell is used as the gas inert to the fuel cell. .

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